US4961049A - Magnetically-coupled apparatus for measuring electrical current - Google Patents

Magnetically-coupled apparatus for measuring electrical current Download PDF

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Publication number
US4961049A
US4961049A US07/281,124 US28112488A US4961049A US 4961049 A US4961049 A US 4961049A US 28112488 A US28112488 A US 28112488A US 4961049 A US4961049 A US 4961049A
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Prior art keywords
secondary winding
signal
current
transformer
winding
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US07/281,124
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English (en)
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Luca Ghislanzoni
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Agence Spatiale Europeenne
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Agence Spatiale Europeenne
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R15/00—Details of measuring arrangements of the types provided for in groups G01R17/00 - G01R29/00, G01R33/00 - G01R33/26 or G01R35/00
    • G01R15/14—Adaptations providing voltage or current isolation, e.g. for high-voltage or high-current networks
    • G01R15/20—Adaptations providing voltage or current isolation, e.g. for high-voltage or high-current networks using galvano-magnetic devices, e.g. Hall-effect devices, i.e. measuring a magnetic field via the interaction between a current and a magnetic field, e.g. magneto resistive or Hall effect devices
    • G01R15/207—Constructional details independent of the type of device used

Definitions

  • the present invention relates to an apparatus of the magnetically coupled type for measuring electrical current which may be A.C. and/or D.C.
  • Galvanomagnetic devices are used as detector components for measuring electrical currents. Detailed information on such devices can be found in the technical literature, and reference may be made, for example, to Siemens' data book entitled “Galvanomagnetic devices” published 1976/1977. There are two different techniques for performing the measurement.
  • the first technique is one in which, at least in theory, there ought to be no need to perform compensation for variations in magnetic flux.
  • the corresponding apparatus for implementing the technique essentially comprises a magnetic circuit including a gap in which the galvanomagnetic device is inserted.
  • the magnetic circuit is excited by current flowing in a winding.
  • Variations in the flux correspond to variations in the input current in accordance with the following equation: ##EQU1## where: B* is the value of the magnetic induction;
  • i is the input current at frequency f
  • ⁇ 2 ⁇ f, i.e. the angular frequency
  • N is the number of turns in the winding
  • a s is the area of the magnetic circuit surrounded by said winding
  • L is the inductance, including the effect of the magnetic circuit.
  • the electrical voltage v i * induced between the output terminals is defined by the following expression which is applicable on the assumption that magnetic leakage (and thus leakage inductance) and also the increase in the effective gap area are negligible: ##EQU2##
  • Equation (4) shows that the induced electrical voltage is directly proportional to the number of turns N and to the angular frequency ⁇ .
  • Apparatuses of this category therefore suffer from the drawback of requiring a very high value of inductance (i.e. a high number of turns) in order to obtain the desired sensitivity for the measuring device: this condition gives rise to a relatively high value for the voltage induced between the terminals of the device and corresponds to behavior which is far from ideal.
  • the second technique of measuring electrical current using galvanometric devices is a technique in which variations of magnetic flux are compensated actively.
  • the corresponding apparatus for implementing the second technique differs from that used for implementing the above-described first technique in that the magnetic circuit includes an auxiliary winding in addition to the main excitation winding.
  • a negative feedback circuit controls the current flowing through said auxiliary winding in such a manner as to provide full compensation for variations in magnetic flux, i.e. so as to obtain a value for the magnetic induction B which is zero or constant.
  • the negative feedback circuit must be designed in such a manner as to have a passband which goes from zero frequency (corresponding to D.C.) up to the desired frequency (for A.C.).
  • the impedance of the measuring device is also very low (and in theory zero).
  • the object of the present invention is to provide a magnetically coupled current measuring apparatus which satisfies practical requirements better than known prior apparatuses for the same purposes, and in particular which:
  • Apparatus in accordance with the present invention uses a third measurement technique which may be referred to as a "passive" (or intrinsic) technique for compensating variations in magnetic flux, and which makes it possible to realize apparatuses (i.e. apparatuses belonging to a third category) whose design and structure are greatly simplified while still maintaining the advantages of apparatuses of the second category.
  • apassive or intrinsic
  • the present invention provides a current measuring apparatus of the magnetically coupled type, the apparatus comprising a transformer provided with:
  • a magnetic circuit defined by a core of ferromagnetic material having a gap and a device placed in the gap for providing a first signal (v i ) which is a function of the magnetic flux existing in the gap;
  • each of the windings being disposed around said magnetic circuit and each including its own number of turns (N p , N s );
  • the apparatus further including:
  • separator means for separating the D.C. component and the low frequency A.C. components in the current to be measured (I) from the high frequency A.C. components (i r ) of the same current;
  • summing means for summing said first and second signals, said summing means thus providing a third signal which is proportional to the current to be measured (I).
  • said separator means for separating the D.C. component and the low frequency A.C. components from the high frequency A.C. components is constituted by said secondary winding which is substantially short circuited.
  • the means providing said second signal is constituted by a very low value impedance, of the order of a few milliohms, inserted in the secondary winding, thereby having substantially no effect on the short circuit operation thereof, with said second signal being defined by the voltage existing across the terminals of said impedance.
  • the impedance looping the secondary winding is constituted by a pure resistance.
  • the means providing said second signal is constituted by an amplifier fed by said secondary winding, with the input and the output of said amplifier sharing a common terminal, the transfer admittance between the input and the output being very high (theoretically infinite), such that the input impedance to the amplifier and the output impedance from the amplifier are very low (theoretically zero), said second signal being defined by the voltage existing between the terminals of the output impedance of the amplifier equivalent to the transfer admittance between the input and the output of said amplifier.
  • the means providing said second signal is constituted by a third winding disposed around said magnetic circuit, said second signal being constituted by the voltage existing across the terminals of said third winding, and said third winding includes a very large number of turns (N ad ).
  • the core of the magnetic circuit is made of non-laminated soft iron.
  • said means for summing said first and second signals is constituted by a wideband operational amplifier which has its input terminals connected to respective output terminals from said means providing said first and second signals, with the other terminals thereof being common.
  • a wideband amplifier amplifies said second signal while a mediumband amplifier amplifies said first signal.
  • the invention also includes other dispositions which appear from the following description.
  • FIG. 1 is a first theoretical circuit diagram of a measuring apparatus in accordance with the invention
  • FIGS. 2 and 3 show two possible practical configurations of the FIG. 1 circuit, for the case where a Hall effect generator is available in the gap in the magnetic circuit of the transformer;
  • FIG. 2A is a detailed circuit diagram of one possible implementation of the circuit shown in FIG. 2;
  • FIG. 4 is the equivalent circuit diagram of the transformer shown in FIGS. 1 to 3;
  • FIG. 5 shows a variant embodiment of the apparatus shown in FIG. 1;
  • FIG. 6 is the equivalent circuit of the configuration shown in FIG. 1;
  • FIG. 7 shows another variant embodiment of the FIG. 1 apparatus.
  • FIG. 1 is a theoretical diagram of a current measuring apparatus in accordance with the invention.
  • T r is a transformer whose magnetic circuit F has a gap E.
  • R is a resistor of very low value, e.g. about 10 m ⁇ .
  • G is a galvanomagnetic device (e.g. a Hall effect generator or any other device providing a signal across its output terminals which is a function of magnetic flux), said device being placed in the gap.
  • a galvanomagnetic device e.g. a Hall effect generator or any other device providing a signal across its output terminals which is a function of magnetic flux
  • ⁇ is an active or passive summing circuit whose output is a function of the input current I to be measured flowing in the primary winding P which is constituted by N p turns, where the secondary winding S has N s turns.
  • FIGS. 2 and 3 show two possible configurations of the circuits shown in FIG. 1 using a Hall effecg generator G h , for example, whose interaction with the magnetic field of the transformer is represented diagrammatically by a dashed line.
  • I h is the current source feeding the generator G h .
  • A is a wideband amplifier.
  • a dc is a mediumband amplifier having very high gain whose input is defined by the voltage due to the Hall effect as made available at the output terminals of the Hall effect generator
  • a ac is a wideband amplifier of medium gain which is sensitive to the high frequency alternating voltage that exists across the terminals of the resistor R.
  • FIG. 2A is a detailed circuit diagram of one possible configuration for the circuit shown in FIG. 2, said circuit diagram showing the transformer T r , the Hall effect generator device G h , the amplifiers A dc and A ac (which are of the type referenced LM 308) together with the resistor R connected across the terminals of the secondary winding. It is assumed that the resistance of the resistor R shown in the circuit of FIG. 2A is 50 m ⁇ and the other circuit components have the following values:
  • the circuit of FIG. 2A also shows a 2N2907-A type PNP transistor and two Zener diodes Z 1 and Z 2 .
  • C D is the decoupled capacitance of a decoupling capacitor for decoupling the capacitance between the primary and the secondary windings.
  • FIG. 4 is an equivalent circuit diagram of the measuring device shown in FIGS. 1 to 3.
  • L l is the leakage inductance
  • L m is the inductance which takes account of the magnetic circuit
  • the D.C. component I dc When the D.C. component I dc is present, it necessarily flows through L m in the above-mentioned equivalent circuit, given that its n 2 R branch relates solely to the "transformer" effect.
  • the current I m is a function of the magnetic flux and is detected by the device G in the form of a voltage signal v i , whereas the current i r may be detected by means of the voltage v r which is induced in the secondary winding S, with i r being related thereto by the equation:
  • the D.C. amplifier A dc does not need a large wideband amplifier (a bandwidth of up to 1 kHz is sufficient in practice), with the total bandwidth being defined by the passband of the A.C. amplifier A ac .
  • the A.C. current i m which takes account of the magnetic circuit effect, includes only low frequency components together with a possible D.C. component, thereby giving rise only to very small variations in the flux in the magnetic circuit and thus justifying the fact that a device in accordance with the invention does not need said flux variations to be compensated.
  • Equation 5 thus shows that by closing the secondary winding substantially on a short circuit (given the very small resistance of the resistor R) it is possible to separate the D.C. components together with the low frequency A.C. components as presented by I m , from the high frequency A.C. components as represented by i r .
  • the signal v i provided by the device G is proportional to the magnetic induction, it follows that this signal and said induction correspond to the D.C. component and to the low frequency A.C. components, whereas the signal v r available from the terminals of the resistor R is proportional to the high frequency components.
  • the voltage v i induced at the terminals of the device G h may be expressed as a function of the voltage v ab between input terminals: ##EQU6##
  • Equation (12b) shows that this maximum value is independent of frequency and that it is inversely proportional to the number of turns N p of the primary winding, and this is in contrast to above-mentioned equation (4) which relates to the first prior art measuring method.
  • the performance of measuring apparatus in accordance with the invention can be further improved by adopting the configuration shown in FIG. 7, i.e. by using a third winding R ad including a very large number of turns N ad and by using the voltage v ad available at the terminals of the winding R ad as a signal proportional to the sum of the high frequency A.C. components of the current I to be measured (represented by the term i r as mentioned above).
  • the voltage v ab across the input terminals of the apparatus can be expressed as being practically equal to n 2 R ⁇ i r .
  • v ad can therefore be calculated from the following ratio: ##EQU12## which makes it possible to write:
  • the number of turns N ad can thus be made as high as possible with the only limits being essentially practical and related to problems of expense and bulk.
  • the FIG. 7 circuit means that the resistance of the resistor R inserted in the secondary winding can be reduced to the point where it is constituted solely by the resistance of the corresponding secondary winding S.
  • FIG. 6 shows a solution which is electrically equivalent to that shown in FIG. 1.

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Measuring Instrument Details And Bridges, And Automatic Balancing Devices (AREA)
  • Measurement Of Current Or Voltage (AREA)
  • Measuring Magnetic Variables (AREA)
  • Measurement Of Resistance Or Impedance (AREA)
US07/281,124 1987-12-11 1988-12-07 Magnetically-coupled apparatus for measuring electrical current Expired - Lifetime US4961049A (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
FR8717313A FR2624617B1 (fr) 1987-12-11 1987-12-11 Appareil de mesure de courants electriques a couplage magnetique
FR8717313 1987-12-11

Publications (1)

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US4961049A true US4961049A (en) 1990-10-02

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US (1) US4961049A (fr)
EP (1) EP0320341B1 (fr)
JP (1) JP2598496B2 (fr)
CA (1) CA1293538C (fr)
DE (1) DE3880280T2 (fr)
FR (1) FR2624617B1 (fr)

Cited By (20)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5146156A (en) * 1989-04-13 1992-09-08 Liaisons Electroniques Mecaniques Lem S.A. Current intensity transformer device for measuring a variable electric current
US5565765A (en) * 1994-07-05 1996-10-15 Vacuumschmelze Gmbh Current sensor operating according to the compensation theorem
US5617019A (en) * 1995-02-23 1997-04-01 Liaisons Electroniques-Mecaniques Lem S.A. Inductive measuring device for measuring alternating current components superposed to a high direct current
US5654630A (en) * 1995-05-11 1997-08-05 Yazaki Corporation Contactless sensor driven by single power supply
ES2113808A1 (es) * 1995-09-29 1998-05-01 Univ Valencia Sensor de corriente de muy baja impedancia y alta estabilidad.
US5892430A (en) * 1994-04-25 1999-04-06 Foster-Miller, Inc. Self-powered powerline sensor
WO2000038347A1 (fr) * 1998-12-18 2000-06-29 Fuba Communications Systems Gmbh Bobine de reactance d'une ligne de transmission a distance
WO2001033233A1 (fr) * 1999-10-29 2001-05-10 Honeywell Inc. Systeme de detection de courant magnetoresistant a boucle fermee avec compensation active du decalage
US20010052843A1 (en) * 1996-11-01 2001-12-20 Richard M. Wiesman Non-invasive powerline communications system
US6411078B1 (en) 1999-01-21 2002-06-25 Tdk Corporation Current sensor apparatus
US6677743B1 (en) 1999-03-05 2004-01-13 Foster-Miller, Inc. High voltage powerline sensor with a plurality of voltage sensing devices
US20050229054A1 (en) * 2004-03-24 2005-10-13 Von Campenhausen Aurel Integrated circuit
EP1965217A1 (fr) * 2007-03-02 2008-09-03 Liaisons Electroniques-Mecaniques Lem S.A. Capteur de courant à boucle ouverte à grande largeur de bande
US20100176798A1 (en) * 2006-08-09 2010-07-15 Koninklijke Philips Electronics N.V. Magnet system for biosensors
US20140176118A1 (en) * 2012-12-20 2014-06-26 Electro-Motive Diesel, Inc. Differential Current Sensor
CN103983832A (zh) * 2010-04-23 2014-08-13 株式会社田村制作所 电流检测器
US20140285180A1 (en) * 2013-03-25 2014-09-25 National Instruments Corporation Circuit to Compensate for Inaccuracies in Current Transformers
CN103983832B (zh) * 2010-04-23 2016-11-30 株式会社田村制作所 电流检测器
US9638722B2 (en) 2013-12-11 2017-05-02 Deere & Company Current sensor and control circuit
EP3206037A1 (fr) 2016-02-15 2017-08-16 C-Sigma S.R.L. Procédé et appareil pour la mesure de courant électrique au moyen d'une configuration à auto-compensation de capteurs de champ magnétique

Families Citing this family (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE9113081U1 (fr) * 1991-10-21 1991-12-12 Siemens Ag, 8000 Muenchen, De
DE4212461A1 (de) * 1992-04-14 1993-10-21 Vacuumschmelze Gmbh Direktabbildender Stromsensor
FR2690993A1 (fr) * 1992-05-06 1993-11-12 Europ Agence Spatiale Détecteur d'intensité de courant unidirectionnel à isolement galvanique, dispositif de mesure d'intensité, convertisseur de courant continu-continu et radar mettant en Óoeuvre un tel détecteur.
DE10011047B4 (de) * 2000-03-07 2010-04-15 Vacuumschmelze Gmbh Direktabbildender Stromsensor
EP1452878A1 (fr) * 2003-02-27 2004-09-01 Liaisons Electroniques-Mecaniques Lem S.A. Capteur de courant électrique
US7309980B2 (en) * 2006-05-08 2007-12-18 Tektronix, Inc. Current sensing circuit for use in a current measurement probe
JP2008289267A (ja) * 2007-05-17 2008-11-27 Hitachi Ltd 電力変換装置およびその制御方法
US11079424B2 (en) * 2018-12-07 2021-08-03 Schneider Electric USA, Inc. Combined low frequency and high frequency current sensor
CN113075442B (zh) * 2021-03-30 2023-03-14 国网宁夏电力有限公司电力科学研究院 电流互感电路和电流互感器
DE102021209537A1 (de) 2021-08-31 2023-03-02 Vitesco Technologies GmbH Transformator

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US3482163A (en) * 1967-05-24 1969-12-02 Tektronix Inc Magnetic signal measuring device including degaussing means
US3916310A (en) * 1973-06-05 1975-10-28 Siemens Ag Electronic measuring instrument arrangement for measuring electrical A-C quantities
US4255705A (en) * 1979-09-24 1981-03-10 General Electric Company Peak detection and electronic compensation of D. C. saturation magnetization in current transformers used in watt hour meter installations
EP0194225A1 (fr) * 1985-02-05 1986-09-10 Lem Sa Transformateur d'intensité pour courant continu et alternatif

Patent Citations (5)

* Cited by examiner, † Cited by third party
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US3482163A (en) * 1967-05-24 1969-12-02 Tektronix Inc Magnetic signal measuring device including degaussing means
US3916310A (en) * 1973-06-05 1975-10-28 Siemens Ag Electronic measuring instrument arrangement for measuring electrical A-C quantities
US4255705A (en) * 1979-09-24 1981-03-10 General Electric Company Peak detection and electronic compensation of D. C. saturation magnetization in current transformers used in watt hour meter installations
EP0194225A1 (fr) * 1985-02-05 1986-09-10 Lem Sa Transformateur d'intensité pour courant continu et alternatif
US4682101A (en) * 1985-02-05 1987-07-21 Lem S.A. Current transformer for direct and alternating current

Cited By (29)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5146156A (en) * 1989-04-13 1992-09-08 Liaisons Electroniques Mecaniques Lem S.A. Current intensity transformer device for measuring a variable electric current
US5892430A (en) * 1994-04-25 1999-04-06 Foster-Miller, Inc. Self-powered powerline sensor
US5565765A (en) * 1994-07-05 1996-10-15 Vacuumschmelze Gmbh Current sensor operating according to the compensation theorem
US5617019A (en) * 1995-02-23 1997-04-01 Liaisons Electroniques-Mecaniques Lem S.A. Inductive measuring device for measuring alternating current components superposed to a high direct current
US5654630A (en) * 1995-05-11 1997-08-05 Yazaki Corporation Contactless sensor driven by single power supply
ES2113808A1 (es) * 1995-09-29 1998-05-01 Univ Valencia Sensor de corriente de muy baja impedancia y alta estabilidad.
US20010052843A1 (en) * 1996-11-01 2001-12-20 Richard M. Wiesman Non-invasive powerline communications system
US7158012B2 (en) 1996-11-01 2007-01-02 Foster-Miller, Inc. Non-invasive powerline communications system
WO2000038347A1 (fr) * 1998-12-18 2000-06-29 Fuba Communications Systems Gmbh Bobine de reactance d'une ligne de transmission a distance
US6707364B1 (en) * 1998-12-18 2004-03-16 Fuba Communications Systems Gmbh Remote feeder reactance coil
US6411078B1 (en) 1999-01-21 2002-06-25 Tdk Corporation Current sensor apparatus
US6677743B1 (en) 1999-03-05 2004-01-13 Foster-Miller, Inc. High voltage powerline sensor with a plurality of voltage sensing devices
US6445171B2 (en) 1999-10-29 2002-09-03 Honeywell Inc. Closed-loop magnetoresistive current sensor system having active offset nulling
US6566856B2 (en) 1999-10-29 2003-05-20 Honeywell International Inc. Closed-loop magnetoresistive current sensor system having active offset nulling
WO2001033233A1 (fr) * 1999-10-29 2001-05-10 Honeywell Inc. Systeme de detection de courant magnetoresistant a boucle fermee avec compensation active du decalage
US20050229054A1 (en) * 2004-03-24 2005-10-13 Von Campenhausen Aurel Integrated circuit
US7203883B2 (en) * 2004-03-24 2007-04-10 Infineon Technologies Ag Integrated circuit
US20100176798A1 (en) * 2006-08-09 2010-07-15 Koninklijke Philips Electronics N.V. Magnet system for biosensors
CN101627311B (zh) * 2007-03-02 2012-06-27 机电联合股份有限公司 高带宽开环电流传感器
US20100097049A1 (en) * 2007-03-02 2010-04-22 Liaisons Electroniques-Mecaniques Lem S.A. High Bandwidth Open-Loop Current Sensor
WO2008107773A1 (fr) * 2007-03-02 2008-09-12 Liaisons Electroniques-Mecaniques Lem S.A. Capteur de courant à boucle ouverte de bande passante élevée
US7977934B2 (en) 2007-03-02 2011-07-12 Liaisons Electroniques-Mechaniques Lem S.A. High bandwidth open-loop current sensor
EP1965217A1 (fr) * 2007-03-02 2008-09-03 Liaisons Electroniques-Mecaniques Lem S.A. Capteur de courant à boucle ouverte à grande largeur de bande
CN103983832A (zh) * 2010-04-23 2014-08-13 株式会社田村制作所 电流检测器
CN103983832B (zh) * 2010-04-23 2016-11-30 株式会社田村制作所 电流检测器
US20140176118A1 (en) * 2012-12-20 2014-06-26 Electro-Motive Diesel, Inc. Differential Current Sensor
US20140285180A1 (en) * 2013-03-25 2014-09-25 National Instruments Corporation Circuit to Compensate for Inaccuracies in Current Transformers
US9638722B2 (en) 2013-12-11 2017-05-02 Deere & Company Current sensor and control circuit
EP3206037A1 (fr) 2016-02-15 2017-08-16 C-Sigma S.R.L. Procédé et appareil pour la mesure de courant électrique au moyen d'une configuration à auto-compensation de capteurs de champ magnétique

Also Published As

Publication number Publication date
EP0320341A1 (fr) 1989-06-14
EP0320341B1 (fr) 1993-04-14
DE3880280T2 (de) 1993-07-29
DE3880280D1 (de) 1993-05-19
JP2598496B2 (ja) 1997-04-09
FR2624617B1 (fr) 1990-05-11
FR2624617A1 (fr) 1989-06-16
CA1293538C (fr) 1991-12-24
JPH01265168A (ja) 1989-10-23

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